Solution of Laplace Integral Equation Using Convolution Theorem

In summary, the conversation discusses solving an integral equation using the Laplace transform and the convolution theorem. The equation is rewritten using the convolution theorem and is solved for the variable y. It is then simplified using basic algebra and partial fractions before being able to invert and obtain the final solution. The final answer is F(t) = 1/5*e^2t - 1/5cos(t) + 3/5sin(t).
  • #1
Trestal
3
0

Homework Statement


By taking the Laplace transform and using the convolution theorem, obtain the solution of the integral equation

Homework Equations


f(t) = sin t + ∫e^(t-u)*f(u) du
integral is from 0 to t

The Attempt at a Solution


I used the following site as a reference for how to construct the problem
http://www.solitaryroad.com/c915.html

I rewrote the equation using the convolution theorem to be this
f(t) = sin t + e^t*f(t)
Letting y = L{f(t)} this becomes
y = 1/s^2 + y/s-1

The website that i referenced you too somehow removes the y and gets the RHS purely in terms of s. I cannot reproduce the simplication the site used on their problem nor can i apply it to my own. I get
y = y(s^2+1)+(s-2)/[(s^2+1)(s-2)]

Hopefully I am just missing something obvious but I am unsure what to do from here. I will continue to play around with it but hopefully someone can nudge me in the right direction.
 
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  • #2
What you are missing is basic algebra!

Solve y = 1/s^2 + y/(s-1) for y and apply the inverse transform.
 
  • #3
Finally got it. Took me hours to work through that but I just couldn't see a solution until you gave me a push. Cheers

Solve for y then solve using partial fractions before being able to invert
Final answer
F(t) = 1/5*e^2t - 1/5cos(t) + 3/5sin(t)

Thanks again!
 

Related to Solution of Laplace Integral Equation Using Convolution Theorem

1. What is Laplace Integral Equation?

The Laplace Integral Equation is a mathematical equation that is used to solve problems in electrostatics and fluid dynamics. It is derived from the Laplace equation, which describes the relationship between the potential and its derivatives in a given system.

2. How is Laplace Integral Equation used in science?

The Laplace Integral Equation is used in various fields of science, such as physics, engineering, and mathematics. It is particularly useful in solving boundary value problems, where the values of a function are known on the boundary of a region and the equation is used to determine the values within the region.

3. What are the applications of Laplace Integral Equation?

The applications of Laplace Integral Equation are numerous, including calculating electric potential and fluid flow in a given system, determining the temperature distribution in a solid object, and solving heat conduction problems. It is also used in image processing, signal analysis, and other fields where solving partial differential equations is necessary.

4. What are the limitations of Laplace Integral Equation?

While the Laplace Integral Equation is a powerful tool in solving various scientific problems, it does have its limitations. It can only be used in linear systems, and it assumes that the underlying physical processes are time-independent. It also does not take into account the effects of turbulence or other non-linear phenomena.

5. Are there any real-world examples of Laplace Integral Equation in action?

Yes, there are many real-world examples of the Laplace Integral Equation being used. For instance, it is used in calculating the electric field and potential in various electronic devices, such as capacitors and resistors. It is also used in modeling the flow of air around an airplane wing and in predicting the temperature distribution in a heated building.

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